The objective of this proposal is to develop an ultrasound particle agglutination (UPA) method for determination of pathogenic bacteria Escherichia coli O157:H7 and Listeria monocytogenes in body fluids, food and environmental samples. The UPA assay is based on the use of ultrasound to significantly increase the sensitivity and reduce time of conventional particle agglutination immunoassay. Ultrasound waves are used for both accelerating and monitoring of the agglutination process. The effective testing of bacteria requires methods of analysis that meet a number of challenging criteria. Bacterial detection methods have to be rapid and very sensitive since the presence of even a single pathogenic organism in the body or food may be an infectious dose. The immunoassay we propose to develop will be implemented in a simple, portable and inexpensive device based on the novel patented cylindrical resonator technology. Significantly, the method can be easily adapted to detect other target objects. Preliminary studies confirmed feasibility of the major innovative components of the proposed technology and it is shown that the new method has significant commercial and scientific potential.